Pacific Northwest sagebrush steppe

Though it is the most widespread of plant ecosystems in eastern Washington, covering 24,000 square miles, the sagebrush-steppe is probably the least understood, and therefore the least appreciated, especially among gardeners. By nature, gardeners like to make things grow, and by the looks of things, not much grows in that desert-like region, except sagebrush. But the sagebrush-steppe region is home to some of most adaptive and intriguing plants on earth, and gardeners can learn much here to apply to eco-friendly rock gardens and xeriscapes.

The region is most strongly defined by its dryness. Lying entirely east of the Cascade Mountains, it receives only eight to12 inches of precipitation each year. Little to none of that comes during the summer, which accounts for the region’s lack of appeal to many gardeners.

Plants in the sagebrush-steppe area survive on a minimum of moisture and make do with some very shallow, rocky soils. Plants tough enough for these conditions include a variety of shrubs, bunch grasses, and forbs. Only near streams or seeps is there enough year-round moisture to sustain clumps of willow, alder, and cottonwood trees.

Artemisia tridentata, big sagebrush, is by far the most common shrub, but other Artemisias include stiff sage, three tip sage, and prairie sage. Other shrubs include bitterbrush, rabbitbrush, and saltbush. These desert shrubs in their soft hues of grays, greens, yellow, and rust hold up in the harshest of conditions and provide refuge for elk, deer, coyote, lizards, and dozens of species of birds and small mammals.

The wide spacing between desert shrubs is a survival technique that allows them to stretch their roots and garner the very small, but necessary amount of water needed to survive the summer. Those spaces are not empty, though. Interspersed among the shrubs grow the equally water- and nutrient-thrifty bunchgrasses and forbs, most of which go dormant during the summer and do not threaten the larger shrubs’ survival.

Unlike sod-forming grasses that spread evenly across the ground to create lawns, bunchgrasses grow in individual clumps. Their extensive root systems absorb and conserve moisture efficiently, and their tufts of stems and narrow leaf blades resist the drying effects of steady wind in the region. As an extra water-conserving measure, bunchgrasses go dormant during the summer months, coming to life only in the wetter seasons of spring and late fall.

Forbs, or wildflowers, are most apparent in the spring, when ground moisture is ample. This is when the land appears brushed with the subtle purples, pinks, and yellows of the native lupines, phlox, sego lilies, cacti, desert parsley, and balsamroot. The blooms of these desert wildflowers last but a few weeks before the plants tuck themselves into their low-lying and water-conserving cushion or mat forms for summer and underground water-absorbing root forms for winter.

Subtler yet are the many ground-hugging mosses, lichens, and the invisible fungi and bacteria that form the region’s “cryptogamic crust.” This ancient crust layer, all but disappearing now because of livestock grazing and human disturbance, is what holds the land’s precious moisture, prohibits invading weeds, and stabilizes its fragile soil.

What can gardeners learn from this land of harsh conditions?

If areas of your property are “like a desert,” create a rock garden to showcase the rich array of extraordinary xeric, or drought-loving, plants.

To conserve water, the smaller of the desert plants grow close to the ground in tight cushion or mat forms, with small and heavily textured or hairy leaves. To fully appreciate these fascinating adaptive features, create rock gardens in raised beds, terraced slopes, or mounded areas to invite close inspection.

Xeric plants require fast draining soil. If the ground is not already dry and gritty, mix a three-inch layer of pea gravel or coarse sand into the top foot of soil. To establish plants, mimic spring conditions of ample moisture, but once they’re established, water only after the top few inches of soil are dry.

 

Further reading

To fully appreciate the magnificence of the sagebrush steppe system:

 

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Tonie Fitzgerald is a WSU/Spokane County extension agent in horticulture and author of Gardening in the Inland Northwest (Washington State University, 2001).